James’ veins are popping off his face. Beyond that, it’s just teeth and snarl. Everyone’s hollering and my legs gave out five minutes ago, but I’m plowing forward because we feed off each other. This is what happens when you shred your quads and accelerate your heart rate through animal-based fitness training. It’s deceptive. Depending on which YouTube video you watch, the Zuu looks simple and playful or brutal and grueling. The latter is the reality.

On all fours we move herdlike through the carpeted room. Then we’re back to frog squats. We break into the bear crawl, another animal movement that strengthens our joints. There’s the gorilla, the iguana, the crocodile, the flea.

“It gets pretty hectic in here,” Dirk, one of the owners, said at the beginning. “If you’re feeling that you’re getting postoperative, get a beverage from the fridge.”

Then what? I wonder. I knew I wouldn’t be “banging it out till the wheels fall off’’ like the rest, but I want at least to walk out of here.

Unification and encouragement are main tenets of the program, so no one lets me bail. Aussie Nathan Helberg, founder of the England-based fitness program, says Zuu is all about liberating movement, helping others and growing culturally. He and the hard-bodied rugby types here to launch the Las Vegas program (free through September), confirm the high-intensity training.

I last 20 minutes. With “no spewing on the floor” a hard-and-fast rule, I make for the door and stand outside only to learn a couple minutes later that Laura, a trainer and my partner in the exercise, is still doing her handstand against the wall. “She won’t come down until you tap her,” Helberg says.

My heart sinks. I failed her. Moving my rubber legs across the room, I tap her on the shoulder and then watch as she and the group bend and lunge their bodies repetitiously in unique ways together, then move into one minute of gorillas.

World Zuu 4985 S. Fort Apache Road, worldzuu.com.